The film stars Vishnu Vishal, Amala Paul, and Saravanan, while Ammu Abhirami, Kaali Venkat, Vinodhini Vaidyanathan, and Ramdoss play supporting roles.
The film features music and a background score composed by Ghibran, cinematography by P. V. Shankar, and editing by San Lokesh.
It tells the story of an aspiring film director who becomes a police officer after his father's death and tries to track down a serial killer.
In the opening scene, two elderly men discover a dead corpse of Samyuktha, a 15-year old school student, who was brutally murdered.
The same day, Ammu is abducted from her birthday party at home and Arun finds her mutilated corpse in their car trunk.
Finding an audio clip from Meera's hearing aid, he traces a piano tune back to a lady magician Annabella George, who performed at all the victims' schools.
Arun finds that Annabella picks students by randomly calling them on to the stage, she then follows, abducts and kills them within the next few days.
Rajamanickam tells that Annabella's real name is Mary Fernandez and her son Christopher who has Werner Syndrome (progeria), a hormonal disorder that causes him to appear aged.
Christopher starts developing feelings for Sophia and he proposes to her, but he is heartbroken when she turns him down, since his condition has rendered him impotent and he cannot have a love life.
Arun discovers that Rajamanickam had pieced information from photographs and he was going to about to say that actually it was Christopher disguised as Mary, who was long dead in an accident.
The media finally reports an end to the murders done by Christopher and Arun gets a chance to make a film about a psychopath fulfilling his dream.
In April 2017, actor Jai signed the project titled Ratsasan, which was set to be produced by C. V. Kumar of Thirukumaran Entertainment.
The album features four songs composed by Ghibran and lyrics written by Umadevi, Ramkumar, Ratnakumar and GKB.
The song written by Umadevi and rendered by Sathyaprakash and Chaitra Ambadipudi received positive reviews from music listeners.
M Suganth from The Times of India, gave a positive review for the soundtrack and stated Kaadhal Kadal Dhana as "a romantic melody, a genre that Ghibran is a master at.
Slow and lullaby-like, the persistent strings in the background are soothing, and despite distinct arrangements, the vocals are pronounced enough to make an impact.
[citation needed] Behindwoods wrote "Watch Ratsasan, the structured and engaging screenplay that makes it an intense psycho thriller", giving the movie 3.25/5.
"[12] Sreedhar Pillai of Firstpost, rated 3 out of 5 stars, stating that "Vishnu Vishal's cop act is superlative but this thriller could've done with some trimming".
[13] India Today rated 3 out of 5 stars, and commented "Vishnu Vishal's Ratsasan' is one of the biggest releases in K-Town this week.
"[14] Film Companion South called it "If you turn a blind eye to the coincidences (say, the plot point around an autorickshaw) and the obvious red herrings (a suspected killer), the bulk of Ratsasan works.
Ghibran's terrific score is the aural equivalent of bad airplane food — it makes your tummy queasy.